1) Field of the Invention
The present invention relates to a library apparatus which stores a large number of cartridges such as magnetic tape cartridges and optical disk cartridges, and which transfers the cartridges through an accessor to a deck for processing a storage medium accommodated within each of the cartridges, and more particularly to a relative flag structure for correcting the position of the storage rack with respect to the accessor, and further to a library apparatus including a relative flag.
2) Description of the Related Art
In general, a library apparatus functions as a large-capacity external storage memory, and a storage rack in its locker stores several thousands of cartridges each accommodating, for example, a magnetic tape as a storage medium, and access such as write/read of recording/recorded data is automatically done in relation to the storage medium within each of the cartridges.
Furthermore, the library apparatus is equipped with the aforesaid storage unit for storing the cartridges, a plurality of magnetic tape decks (which will be referred hereinafter to as decks) for conducting access such as write/read of recording/recorded data with respect to a storage medium (magnetic tape) within a cartridge, and an accessor (cartridge transferring robot) for performing the conveyance of the cartridges between the storage rack and the decks.
Commonly, this library apparatus is made up of a storage unit having a storage rack for storing a large number of cartridges, a drive unit incorporating decks, an accessor unit functioning as a garage for accessors, a unit including a controller or the like for controlling the accessors, and other units.
Each of these units is constructed as being one locker, and the arrangement of the whole library apparatus relies on the connections among a plurality of lockers (units). In addition, with the plurality of lockers being in connection, a traveling passage for the accessors is defined in these lockers to penetrate them.
In the library apparatus thus arranged, in response to an access request to one cartridge from a host unit or the like, the accessor travels within the passage to come to the storage rack to search a directing cartridge there, and subsequently, a hand mechanism grips that cartridge and transfers it to the deck for insertion into the deck.
With these operations, in that deck, given processing is done in relation to the storage medium (magnetic tape) within the inserted cartridge. After the completion of the processing, the cartridge discharged from the deck is again gripped by the hand mechanism and conveyed by the accessor up to the storage rack to be stored at a given position.
In a prior art, for allowing the accessor to accurately detect the position of each of cells of the storage rack storing a large number of cartridges, relative flags (for example, see reference numeral 72 in the upper section of FIG. 30) prepared separately from the storage rack have been placed at at least three portions on both sides of the storage rack in the storage unit.
At the initial operation, the accessor reads out the aforesaid relative flags to detect the position of the whole storage rack to recognize the compartments of all the cells as a plane, and establishes meshes, whose number is equal to the number of the cells, to retain the center coordinates of the compartments of the respective cells as a table. Thereafter, the accessor reads out the center coordinate of the compartment of a given cell, thereby carrying out the insertion/extraction operations of a cartridge in relation to that given cell.
However, as shown in the upper section of FIG. 30, when the relative flags 72 are located at both sides of the storage rack 13, the installation area, i.e., volume, of the locker (storage unit) increases to impair the cartridge storage efficiency in the library apparatus, which refuses the requirements for the size reduction of the library apparatus. In addition, at the initial operation, the distance that the accessor 7 travels among a plurality of relative flags increases, with the result that the initial operation takes a longer time.
In the prior library apparatus, a dedicated cartridge delivering and receiving mechanism is provided at every deck, and the insertion/extraction of the cartridge into/from the deck are done through the use of this cartridge delivering and receiving mechanism. That is, the accessor is not made to directly carry out the insertion/extraction of the cartridge into/from the deck.
Recently, for the purpose of the size and cost reduction of the library apparatus, requirements have arisen for enabling the accessor to directly conduct the insertion/extraction of the cartridge with respect to the deck without the interposition of the cartridge delivering and receiving mechanism. For meeting the requirements, in addition to enhancing the control accuracy of the hand mechanism of the accessor, the high-accuracy positioning relative to the deck is essential, and the error correction at the initial step (initial operation) becomes unavoidable, and even attention should be paid to the shortening of the time taken for the initial operation.